1. Field of the Invention
The present invention relates to an illumination apparatus used in an optical information reading apparatus for reading optical information such as a bar code and a QR code.
2. Description of the Related Art
Now that traceability is widespread, an optical information reading apparatus is installed in a factory, a physical distribution complex and the like to decode optical information such as a bar code or an optical code given to a product or a commodity. This type of optical information reading apparatus is called a “bar code reader” or a “code reader”.
The bar code reader irradiates the optical information with laser light, visible light or infrared light to take in reflected light by an optical reading element (image pickup element). Analysis of information recorded in the optical information is performed from the picked-up image that has been taken in.
The bar code reader includes illumination LEDs as described in Japanese Unexamined Patent Publication No. 2008-33465, and takes in the optical information while illuminating a visual field range with these illumination LEDs. In the case where it is difficult to read the optical information by internal illumination of the bar code reader in some surface textures and work environments of a work, external illumination separate from the bar code reader is used (Japanese Unexamined Patent Publication No. H11-338966).
Although it is generally considered that the bar code reader controls the external illumination, the use of the external illumination does not solve all problems, and delicate control over lighting timing, how to throw light in the external illumination, light intensity and the like is often necessary, which limits the control of the external illumination.
Specifically, it is generally known that capability of the bar code reader to read the optical information largely varies, depending on an irradiation direction of the light to the work. Particularly, when reading the optical information (the bar code or the QR code) directly inscribed on the work, which is called direct part marking, even if the optical information originally has enough inscribing quality to be read, the reading may become unstable, or may be disabled, depending on the direction at which the light is thrown to the work. From this, an external illumination unit capable of partial illumination, which can change a lighting portion of a plurality of illumination LEDs has been launched. Such an external illumination unit is connected to the bar code reader, and upon receiving a lighting command from this bar code reader, the external illumination unit lights up.
A usage environment of the bar code reader varies depending on the user, and development of the bar code reader has been carried out with this in mind. In the case where the external illumination unit is used, if the external illumination unit can perform illumination in as various lighting patterns as possible, stable reading can be realized to the work requiring fine reading, such as the work subjected to the above-described direct part marking.
However, in order to realize the various lighting patterns, partial illumination areas in which the illumination LEDs of the external illumination unit can be arbitrarily controlled so as to be lighted and lighted out need to be increased, and thus, in order to control the lighting and the lighting-out on the basis of each of the increased partial illumination areas, a control line corresponding to each of the areas needs to be prepared. This leads to complication of the control, and wiring connecting the bar code reader and the external illumination unit becomes very complicated.
Obviously, when followability of speeding-up of a production line of a factory where the bar code reader is installed, and an applicable range of the bar code reader are intended to be increased, enhancement in flexibility and responsiveness of the control of the external illumination is sought.